From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753318AbeDSSad (ORCPT ); Thu, 19 Apr 2018 14:30:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:34280 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752086AbeDSSab (ORCPT ); Thu, 19 Apr 2018 14:30:31 -0400 Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM To: Mikulas Patocka , David Miller , Andrew Morton , linux-mm@kvack.org Cc: eric.dumazet@gmail.com, edumazet@google.com, bhutchings@solarflare.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, dm-devel@redhat.com, Laura Abbott References: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> <20180418.134651.2225112489265654270.davem@davemloft.net> From: Vlastimil Babka Message-ID: Date: Thu, 19 Apr 2018 20:28:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/19/2018 06:12 PM, Mikulas Patocka wrote: > From: Mikulas Patocka > Subject: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM > > The kvmalloc function tries to use kmalloc and falls back to vmalloc if > kmalloc fails. > > Unfortunatelly, some kernel code has bugs - it uses kvmalloc and then > uses DMA-API on the returned memory or frees it with kfree. Such bugs were > found in the virtio-net driver, dm-integrity or RHEL7 powerpc-specific > code. > > These bugs are hard to reproduce because vmalloc falls back to kmalloc > only if memory is fragmented. > > In order to detect these bugs reliably I submit this patch that changes > kvmalloc to always use vmalloc if CONFIG_DEBUG_VM is turned on. > > Signed-off-by: Mikulas Patocka Hmm AFAIK Fedora uses CONFIG_DEBUG_VM in their kernels. Sure you want to impose this on all users? Seems too much for DEBUG_VM to me. Maybe it should be hidden under some error injection config? > --- > mm/util.c | 2 ++ > 1 file changed, 2 insertions(+) > > Index: linux-2.6/mm/util.c > =================================================================== > --- linux-2.6.orig/mm/util.c 2018-04-18 15:46:23.000000000 +0200 > +++ linux-2.6/mm/util.c 2018-04-18 16:00:43.000000000 +0200 > @@ -395,6 +395,7 @@ EXPORT_SYMBOL(vm_mmap); > */ > void *kvmalloc_node(size_t size, gfp_t flags, int node) > { > +#ifndef CONFIG_DEBUG_VM > gfp_t kmalloc_flags = flags; > void *ret; > > @@ -426,6 +427,7 @@ void *kvmalloc_node(size_t size, gfp_t f > */ > if (ret || size <= PAGE_SIZE) > return ret; > +#endif Did you verify that vmalloc does the right thing for sub-page sizes? Shouldn't those be exempted? > return __vmalloc_node_flags_caller(size, node, flags, > __builtin_return_address(0)); >